A digital image is a representation of a two-dimensional picture or graphics as a finite set of digital values, called picture elements or pixels. Typically, the pixels are stored in computer memory as a raster image or raster map expressed in a two-dimensional array of integers. These values are often transmitted or stored in a compressed form. Digital images can be created by a variety of input devices and techniques, such as digital cameras, scanners, airborne radar, and more. They can also be synthesized from arbitrary non-image data, such as mathematical functions or three-dimensional geometric models in computer graphics, for example.
Common formats for digital image files include JPEG (Joint Photographic Experts Group), GIF (Graphics Interchange Format), and PNG (Portable Network Graphics). However, these digital image formats are not compatible with XML (extensible Markup Language), a text-based format that has increasingly become an important format for many World Wide Web or Internet technologies. These digital image files cannot be easily embedded within XML and require a cumbersome re-encoding process that changes the binary digital image data into a format such as Base 64 that is compatible with XML. These typical re-encoding processes greatly increase processing time as well as demanding larger network bandwidth during electronic transmission.